Variable voltage transformer



Oct. 6, 1964 N. N. BOJARSKI 3,152,311

VARIABLE VOLTAGE TRANSFORMER Original Filed Nov. 8, 1957 v 2 Sheets-Sheet l INVENTOR. uonasm N. BOJARSKI BY W6W ATTORNEYS Oct. 6, 1964 N. N. BOJARSKI 3,152,311

VARIABLE VOLTAGE TRANSFORMER Original Filed Nov. 8, 1957 2 Sheets-Sheet 2 FIG. 5

INVENTOR. NORBERT N. BOJARSKI ATTORNEYS United States Patent 3,152,311 VARIABLE VOLTAGE TRANSFORMER Norbert N. Bojarski, Rochester, N.Y., assignor, by mesne assignments, to L.R. Power Corp., Rochester, N.Y., a corporation of New York Original application Nov. 8, 1957, Ser. No. 695,394. Divided and this application Nov. 9, 1961, Ser. No. 158,630

3 Claims. (Cl. 336-132) This application relates generally to the electrical control art, and more particularly to 'a new and useful variable voltage transformer. This application is a division of Serial No. 695,394, filed November 8, 1957, now abandoned in view of continuation application Serial No. 179,831, filed February 8, 1962.

It is an object of this invention to provide an efficient, multi-purpose transformer adapted to produce an output voltage smoothly and continuously variable in infinitesimal increments, and which does not require brushes or other current-carrying moving parts.

Another object of this invention is to provide a variable voltage transformer wherein the polarity of the output voltage can be reversed.

Still another of this invention is to provide a variable voltage transformer wherein the primary reluctance is independent of the output voltage setting.

A variable voltage transformer constructed in accordance with my invention is characterized by the provision of a transformer core having a primary and two secondary legs, a primary winding on the primary leg, a secondary winding on at least one of the secondary legs, and a rotary magnetic armature divided into sections independently movable to divert primary flux from one of the secondary legs to the other thereof, thereby to vary the relative reuctance of the magnetic circuits comprising the secondary legs to vary the output voltage, the reluctance of the primary magnetic circuit being independent of the positional adjustment of the movable armature.

The foregoing and other objects, advantages and characterizing features of a variable voltage transformer constructed in accord with my invention will become clearly apparent from the ensuing detailed description of certain illustrative embodiments thereof, taken together with the accompanying drawings illustrating such embodiments wherein like reference numerals denote like parts throughout the various views and wherein:

FIG. 1 is a generally diagrammatic view of an illustrative embodiment of the transformer of this invention;

FIGS. 2 and 3 are fragmentary views thereof illustrating different positions of the movable section;

FIG. 4 is a perspective view of the armature construction;

FIG. 5 is a fragmentary sectional view of a transformer incorporating the movable armature sections of FIG. 4; and

FIGS. 6 and 7 are fragmentary, generally diagrammatic views thereof illustrating different positions of the movable sections.

Referring now to the illustrative embodiment shown in the accompanying drawing, a variable voltage transformer constructed in accordance with my invention comprises a transformer core 100, having a primary leg 200 and a pair of secondary legs 300 and 300', a primary winding 12 being placed on leg 200 with secondary windings 15 and 16 placed on legs 300 and 300', respectively. The primary leg preferably has a cross sectional area equal to that of each secondary leg, all other things being equal, for maximum utilization of transformer capacity. The outer end face of primary leg 200 is concave and semicircular in form, and secondary legs 300 3,152,311 Patented Oct. 6, 1964 "Ice and 300' are extended, as at 310 and 310, respectively, to present semicircular, concave end faces drawn on the same radius as the end face of leg 200.

A movable section 210 of generally cylindrical form having the radius of the primary and secondary leg end faces is arranged for working contact therewith. To this end, armature 210 is mounted on a shaft 212 for rotation about the axis thereof, and a sector 211 is removed from armature 210. Preferably, the magnetic section remaining in armature 210 is sufficient to have simultaneous working contact with all of the end face of primary leg 200 and with one half the end face of each secondary leg 360, 300. Of course, armature 210 can be formed to this shape in any desired manner.

Armature 210 is adapted to be rotated about the axis of shaft 212, as by a control knob indicated in broken lines at 213. When in the extreme position illustrated in FIG. 1, armature 210 diverts all of the primary flux to secondary leg 310', as indicated by the arrow. When in its opposite extreme position illustrated in FIG. 2, armature 210 diverts the primary flux to secondary leg 310, and when in its neutral position illustrated in FIG. 3, the primary flux is divided equally between the secondary legs. The series connected secondary windings 15 and 16 will produce a net output voltage, which is smoothly and continuously variable in infinitesimal increments between no voltage and a maximum of either polarity and they can be wound in opposition with either an equal or unequal number of turns, or in an additive sense with an unequal number of turns, or one thereof can be dispensed with.

In any case, the total secondary end face area in working contact with armature 210 remains constant, as does the primary end face area, whereby the primary reluctance is independent of variations in the output voltage, and the primary area in working contact with armature 210 preferably equals such total working secondary area.

Where a still finer adjustment in voltage ratio is desired, the movable diversion element or armature can be split or divided to comprise independently movable sections. Thus, referring for example to the embodiment illustrated in FIGS. 47, there is provided an armature comprising a first movable section 210' and a second section 210" movable relative thereto, the armature being split, to provide the two sections, in a plane containing the three legs of the core.

The sections 210' and 210" provide a total armature section corresponding to armature 210, whereby the total secondary end face area in working contact with the two armature sections remains constant, and the primary end face area in contact therewith also remains constant, as previously discussed. The relative thickness or volume of the sections 210' and 210" is determined by the degree of control which is desired. In other words, the two sections have different cross sectional areas, in a ratio selected to provide the differential necessary to achieve the desired fineness of control. In operation, the larger section 210 can be mounted on shaft 212 for rotation by means of a knob 213, while the smaller section can be mounted on a coaxial shaft 212' for actuation by a coaxial knob 213'.

It is believed that the operation of this embodiment is clear from the foregoing and the detailed description of the previous embodiments. As illustrated in FIGS. 6 and 7, in addition to rotating the armature to selectively divert the magnetic flux as desired between the two secondary legs, or entirely into one of them, it is possible to independently rotate the control elements 210' and 210" to provide a still finer degree of control. The main section 210' is moved in the manner described in connection with the embodiment of FIGS. 1-3 to provide a 3 relatively coarse adjustment, and the minor section 210" can be moved to a different position providing a fine adjustment modifying the main adjustment.

It is contemplated that the transformer of this invention will find wide utility wherever it is desired to vary the output voltage smoothly and continuously and without energy losses associated with rheostat and other conventional control elements. For example, it is thought that it would be highly useful in controlling the heating elements of electric stoves. In such cases, reversal of polarity probably would not be utilized, and the primary voltage could be used as a base. To this end, the transformer can be readily connected as an auto transformer, the primary being tapped into the secondary. By such means, variations between the two extremes would comprise variations above and below the primary voltage as a base, with the output voltage being of constant polarity.

While only certain illustrative embodiments of my invention are described in detail herein, it will be appreciated that my invention is not necessarily limited to the details thereof but includes variations and modifications falling within the scope of the appended claims.

Having completely disclosed and described my invention, together with its mode of operation, what I claim as new is as follows:

1. A variable voltage transformer comprising, a transformer core having a primary leg and two secondary legs, a primary winding on said primary leg, a secondary winding on at least one of said secondary legs, and a rotary magnetic armature coupling said primary leg with at least one of said secondary legs in working contact therewith, said armature being divided into independently movable rotary sections each overyling said primary leg and portions of at least one of said secondary legs in working contact therewith, the composite total area of said secondary legs contacting each of said armature sections and coupled thereby to said primary leg being substantially constant for all working positions of said armature sections.

2. A transformer as set forth in claim 1, wherein there are separate secondary windings on said secondary legs, said secondary windings having different numbers of turns and being connected in series with their voltages mutually additive.

3. A transformer as set forth in claim 1, wherein at least two of said armature sections are of mutually different cross-sectional area to provide relatively coarse and relatively fine adjustments for corresponding rotary movements thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,414,248 Armor Apr. 25, 1922 2,361,738 Bird Oct. 31, 1944 2,564,484 Kuehni Aug. 14, 1951 2,568,587 MacGeorge Sept. 18, 1951 2,692,357 Nilson Oct. 19, 1954 2,750,536 Gomonet June 12, 1956 FOREIGN PATENTS 14,591 France Nov. 6, 1911 777,638 France Dec. 5, 1934 

1. A VARIABLE VOLTAGE TRANSFORMER COMPRISING, A TRANSFORMER CORE HAVING A PRIMARY LEG AND TWO SECONDARY LEGS, A PRIMARY WINDING ON SAID PRIMARY LEGS, AND A ROTARY MAGNETIC ARMATURE COUPLING SAID PRIMARY LEG WITH AT LEAST ONE OF SAID SECONDARY LEGS IN WORKING CONTACT THEREWITH, SAID ARMATURE BEING DIVIDED INTO INDEPENDENTLY MOVABLE ROTARY SECTIONS EACH OVERYLING SAID PRIMARY LEG AND PORTIONS OF AT LEAST ONE OF SAID SECONDARY LEGS IN WORKING CONTACT THEREWITH, THE COMPOSITE TOTAL AREA OF SAID SECONDARY LEGS CONTACTING EACH OF SAID ARMATURE SECTIONS AND COUPLED THEREBY TO SAID PRIMARY LEG BEING SUBSTANTIALLY CONSTANT FOR ALL WORKING POSITIONS OF SAID ARMATURE SECTIONS. 